BAGHDAD — Kurdish and Iraqi forces backed by American airstrikes took control of the Mosul Dam, Iraq's military said Monday.

The U.S. military had launched more than 20 air strikes around the area over the last several days, allowing Kurdish and Iraqi counterterrorism forces to push militants off the dam.

Militants seeded the area with roadside bombs, making progress slow. About 150 improvised explosives were found by ground forces, according to Iraq's military.

The new American strikes suggest an incremental expansion of the U.S. mission, which began more than a week ago to prevent militants from overrunning Irbil, the capital of the Kurdish region, and to save Yaziri refugees trapped on a mountain to escape the Islamic State militants.

The air campaign around the dam has allowed Kurdish forces to begin retaking territory seized by the militants, also known as the Islamic State of Iraq and the Levant. The group shortened its name to the Islamic State.

President Obama sent a letter to Congress on Sunday explaining his authorization of the strikes.

"The failure of the Mosul dam could threaten the lives of large numbers of civilians, endanger U.S. personnel and facilities, including the U.S. Embassy in Baghdad, and prevent the Iraqi government from providing critical services to the Iraqi populace," Obama said in the letter.

Obama emphasized that the mission is limited in "scope and duration."

Militants seized the dam this month, gaining control over electricity distributed to much of northern Iraq and the capability to flood communities downriver.

The U.S. military used a mix of aircraft and drones in Sunday's strikes, destroying or damaging seven Humvees, two armored personnel carriers and a militant checkpoint.

A Shiite fighter loyal to Iraqi cleric Moqtada al-Sadr holds a position in support of the Iraqi army during a fight against Islamic State militants in the Jurf al-Sakher district on Aug. 18 outside Baghdad.
Ali Al-Saadi, AFP/Getty Images

An Iraqi Yazidi woman sits with a child Aug. 17 under a bridge where displaced people of this religious minority found refuge after Islamic State militants attacked the town of Sinjar.
Ahmad al-Rubaye, AFP/Getty Images

Supporters of Prime Minister Nouri al-Maliki rally in Baghdad. Tanks and Humvees were positioned on Baghdad bridges and at major intersections with security personnel more visible than usual as pro-Maliki demonstrators pledge their allegiance to him. The placard reads, "al-Maliki is our choice."
Karim Kadim, AP

Iraqis chant pro-government slogans in support of embattled Prime Minister Nouri al-Maliki in Baghdad on Aug. 11. Al-Maliki is in a struggle to keep his job after Iraqi President Fouad Massoum nominated deputy speaker of the parliament Haider al-Abadi to replace him.
Hadi Mizban, AP

Iraqi army armored vehicles patrol a street in Baghdad, amid tighter security after Iraq's prime minister said he would sue the president in a desperate bid to cling to his job.
Sabah Arar, AFP/Getty Images

Peshmerga forces hand out water bottles and show the way to displaced Iraqi families from the Yazidi community as they cross the Iraqi-Syrian border at the Fishkhabur crossing, in northern Iraq.
Ahmad Al-Rubaye, AFP/Getty Images

A displaced Iraqi boy from the Yazidi community crosses the Iraqi-Syrian border in northern Iraq. Many from the Yazidi, besieged by jihadists on a mountain in northern Iraq have safely escaped to Syria.
Ahmad Al-Rubaye, AFP/Getty Images

An Iraqi Yazidi, who fled her home a week ago when Islamic State militants attacked the town of Sinjar, sits with a baby, on Aug. 10, in a building under construction where Yazidis found refuge in the Kurdish city of Dohuk.
Ahmad Al-Rubaye, AFP/Getty Images

Iraqis Yazidis, who fled their homes a week ago when Islamic State militants attacked the town of Sinjar, sit on makeshift beds inside a building in the Kurdish city of Dohuk in Iraq's autonomous Kurdistan region where Yazidis found shelter.
Ahmad Al-Rubaye, AFP/Getty Images

Displaced Iraqis from the Yazidi community settle at a camp at Derike, Syria. Kurdish authorities at the border believe some 45,000 Yazidis passed the river crossing in the past week and thousands more are still stranded in the mountains.
Khalid Mohammed, AP

Female members of the Kurdistan Workers' Party take position on the front line in Makhmur, south of Arbil, the capital of the autonomous Kurdish region of northern Iraq where clashes with Islamic State militants are ongoing on Aug. 9.
Safin Hamed, AFP/Getty Images

An image from British broadcaster Sky television shows Kurdish soldiers battling militants from the Islamic State of Iraq and the Levant on June 18 near Jalula, Iraq. Kurdish security forces fought the Sunni militants, using heavy artillery and rockets to attack their positions.
Sky via AP

A photograph released on June 17 by Albaraka News allegedly shows a militant fighter from the Islamic State of Iraq and the Levant tying up a captured Iraqi soldier at an undisclosed location near the border between Syria and Iraq on June 12.
Albaraka News via epa

A photograph released on June 17 by Albaraka News allegedly shows fighters from the Islamic State of Iraq and the Levant inspecting vehicles belonging to the Iraqi army after they were captured at an undisclosed location near the border between Syria and Iraq.
Albaraka News via epa

Men flash victory signs as they leave a recruiting center to join the Iraqi army in Baghdad. Young Shiite men are joining the army to battle a Sunni militant force advancing from the north.
Khalid Mohammed, AP

Militants parade down a main road in Mosul. Days after Iraq's second-largest city fell to the militant fighters, some Iraqis are already returning to Mosul, lured back by insurgents offering cheap gas and food, restoring power and water and removing traffic barricades.
AP via Twitter

A photograph from a militant website appears to show militants from the al-Qaeda-inspired Islamic State of Iraq and the Levant taking aim at captured Iraqi soldiers wearing civilian clothing after capturing a base in Tikrit. ISIL has posted photos that appear to show its fighters shooting dead dozens of captured Iraqi soldiers in a province north of the capital Baghdad.
AP

An Iraqi army armored vehicle destroyed during fighting with militants sits on a street on June 12 in Mosul. Militants belonging to the Islamic State of Iraq and the Levant have captured Tikrit and Mosul after soldiers and security forces abandoned their posts.
AP

Teenagers ride on an armored vehicle belonging to the Iraqi army in Tikrit on June 11. Al-Qaida-inspired militants seized effective control Wednesday of Saddam Hussein's hometown of Tikrit, expanding their offensive closer to the Iraqi capital as soldiers and security forces abandoned their posts following clashes with the insurgents.
AP

The militants captured an array of U.S. military equipment from Iraqi forces in June when four divisions collapsed in Mosul after the radical forces attacked the city. The equipment gave Islamic State fighters an advantage in firepower, but they're vulnerable to attack from the air.